For example, in the apparatus disclosed in Patent Literature 1, a plurality of sheet products is supplied one by one at a supplying position. The sheet products comprise plastic bags. The supplied plastic bag is fed to a corner-cut position and an opening position so that the plastic bag is corner-cut by a cutting blade and opened by an opening device. Subsequently, the plastic bag is fed to a heat-seal device, an accessory is inserted in the plastic bag, and the plastic bag and the accessory are heat-sealed by the heat-seal device.
In this case, it is necessary to first supply a plurality of the sheet products one by one. Some apparatuses which achieve this have been proposed. For example, in the apparatus disclosed in Patent Literature 2, sheet products are stacked with each other and fed by a feeding belt. The sheet products comprise wrappers. Further, an additional belt is disposed on upper side of the feeding belt, pressed against an uppermost wrapper, and driven at the speed higher than the feeding belt. The uppermost wrapper is moved forward in advance due to the speed difference to be separated from the subsequent wrappers. Therefore, the wrappers are supplied one by one. In this respect, the same is true of the apparatus disclosed in Patent Literature 3.
The reason why the uppermost wrapper is moved forward in advance due to the speed difference is friction force. The friction force is generated between the additional belt and the uppermost wrapper, and it is higher than friction force between the uppermost wrapper and the next wrapper. When there is the speed difference, the uppermost wrapper is moved forward in advance due to the difference between the friction forces.
However, the friction force is different depending on the material of the wrapper and can also be changed by other factors. The uppermost wrapper is not always moved forward in advance due to the difference between the friction forces. Sometimes, the uppermost wrapper is not separated from the next wrapper, and as a result the both are supplied at the same time.
Therefore, an object of the present invention is to provide a sheet product supplying apparatus for supplying a plurality of sheet products one by one, wherein the sheet products are prevented from being supplied at the same time.